1. Field of the Invention
This invention relates to a device and a method for the preservation of lawn grass on a putting green of a golf course or other plants. More particularly, this invention relates to a green preserving device capable of maintaining the putting green at an optimum temperature for raising plants by circulating heated fluid through an underground pipe laid under the putting green.
2. Description of the Prior Art
There has been conventionally proposed a green heat-up system in which the terrestrial temperature is raised to force the growth of the lawn grass on the putting green in Japanese Utility Model Application Public Disclosure No. SHO 62-102342(A). This prior art system is composed by laying a spiral or zigzag-form pipe under the putting green so as to flow water or air warmed by geothermal heat through the underground pipe.
However, such a heat-up system utilizing geothermal heat has not generally been used to increase the terrestrial temperature. This is because the heat is too low to sufficiently warm the entire area of the putting green for growing the lawn grass. The conventional heat-up system is therefore restricted in the area in which it can be used.
The inventor of the present invention has already proposed a method for heating the putting green of a golf course in which a fluid heated by a boiler is circulated through a supply pipe, a heat radiation pipe laid under the putting green and a return pipe so that the heat of heated fluid is radiated from the radiation pipe to warm the putting green. (Japanese Pat. Appln. Pub. Discl. No. HEI 62-210929(A)).
Though the proposed method can a sufficient heat energy, it however entails a disadvantage in that air is easily produced in the heat radiation pipe when the heat of the heated fluid flowing through the radiation pipe is radiated. The air thus produced causes the so-called air hammer phenomenon, and leads to a problem of bringing about a sudden change of temperature in the radiation pipe. The air hammer phenomenon appears in not only the radiation pipe, but in the return pipe, and is apt to administer impulses, particularly to a joint portion between a large pipe and a small pipe, consequently causing the leakage of fluid or the bursting of the pipe. Thus, the system based on the proposed method has a problem in durability.
Furthermore, since the maintenance of the system for practicing the proposed method costs a great deal, the system is not commercially practicable. Besides, the air hammer phenomenon, which brings about a sudden change in temperature exerts a baneful influence upon the growth of the lawn grass on the putting green.